Direction finder



1934- E. BELLINI 1,983,729

DIRECTION FINDER Fild June 12, 1930 INVENTOR ETTORE BEL INI ATTORNEY Patented Dec. 11, 1934 PATENT OFFICE DIRECTION FINDER Ettore Bellini, Paris,

France, asslgnor to Compagnie' Generalc dc Telegraphic sans Fil, Paris,

France, a corporation of France Application June 12, 1930, Serial No. 460,574 In France June 25, 1929 6 Claims.

It is well known that in radiogoniometry the direction of a transmitting station is obtained by turning the loop (or the movable coil in a radiogoniometer Bellini Tosi) until the extinction of the sound has been accomplished.

This extinction may be imperfect due to two reasons: (1) The superposition on the direct wave of a reflected or refracted wave which arrives in a different direction and with a different phase than the phase of the direct wave. There does not appear to exist a remedy for this cause of extinction, except for particular cases. (2) The superposition on the action of the loop of a vertical effect, that is of the action of the loop itself (or of the action of two fixed loops) functioning in auxiliary manner as vertical antenna.

The invention which is the object of the present patent aims at the elimination of the imperfection on the extinction due to the second cause.

An understanding of the invention will be had from the following description, and therefrom when read in connection with the attached drawing, in which,

Figure 1 shows a directional aerial system including means for increasing the directivity of the direction finder; while,

Figures 2 to 5 inclusive show modifications of the arrangement of Figure 1.

Let C (Fig. 1) be a loop whose center point M is connected to the earth T by a thick conductor L. If the self-inductance and the resistance of this conductor L is strictly zero, the extinction should be perfect, supposing that the cause No. 1 does not exist. In actuality, the self-inductance and the resistance, although very small, can never be zero. It follows therefrom that transmitting stations located very close to the radiogoniometer will not produce sharp extinctions or null points in the radiogoniometer receiving characteristics.

In accordance with the present invention, a sharp extinction is accomplished in this case by having the current of a detuned vertical antenna A influence through an inductance B and an inductance B, the center connection L of the loop C to ground as shown in Figure 2. By varying the sign of the mutual inductance and the coupling between the coils B and B" respectively, inserted in the antenna lead-in and in the center connection L, there is found a position for which the extinction is absolute.

The condition essential for accomplishing this result consists in that the effective height of the auxiliary antenna A is greater than the height of the loop C functioning as a vertical antenna.

If possible, the vertical antenna must be placed inthe very axis of the loop. If this is not feasible, the vertical aerial must be placed far enough away from the loop to insure that the feeble current flowing through the vertical antenna exerts no appreciable action on the loop.

In the case where the connections of the loop to the amplifier D are as indicated in Fig. 3, the action of the vertical antenna is effected according to the diagram of the same figure wherein the same letters designate the same elements as in the previous figures.

In the case of the radiogoniometer Bellini-Tosi, the auxiliary antenna A will be connected either as shown in Fig. 4, or as indicated in Fig. 5. In Fig. 4 the antenna coil B influences inductively the coil B, inserted in aconnection between the center of the inducing loops C and C and the earth, the center of the exploring coil C" being likewise grounded, while the input side of amplifier D is connected to one of the armatures of the tuning condenser S. In Fig. 5, coil B is inserted in the ground connection of exploring coil C".

In each arrangement a receiver R which may include amplifiers and a rectifier is connected to the output terminals of the tube D. It is well understood that the invention is subject to numerous variants in its practical application outside of those given above by way of non-limiting examples.

I claim:

1. In directional receiving systems the combination of a. directional aerial circuit, an aperiodic non-directional aerial circuit, a connection between the electrical midpoint of the directional aerial circuit and ground, an inductive coupling between said non-directional aerial and said connection for introducing non-directional aerial effects from said aperiodic non-directional aerial circuit into said connection, and receiving apparatus including a thermionic tube having its input elements associated with said aerial circuits.

'2. In an aerial system the combination of an aperiodic non-directional radiant energy responsive device, a directional radiant energy responsive device, an inductance connecting the electrical midpoint of said directional radiant energy responsive device to ground and an inductance in said non-directional radiant energy responsive device coupled to said first named inductance.

3. In radio apparatus the combination of a frame aerial, a non-resonant vertical aerial, a thermionic tube, means for tuning said frame aerial, a connection between the electrical mid- 55 point of said frame aerial and ground, an inductance in said connection, an inductance in said non-resonant vertical aerial coupled to said first named inductance, a connection between one terminal of said tuning means and the control electrode of said thermionic tube and a connection between the filament of said thermionic tube and ground.

4. In a directional aerial system the combination of a frame aerial, a non-resonant vertical aerial including an inductance, a connection including a second inductance between the electrical midpoint of the frame aerial and ground and means for introducing compensating current in said last connection including said inductance in said non-resonant vertical aerial coupled to said inductance in said ground connection.

5. In directional receiving systems the combination of a frame aerial circuit, a variable capacity in said circuit for tuning said circuit to the signal frequency, a relay tube having anode, cathode and control electrodes, a non-resonant vertical aerial including an inductance, an'inductance connecting the electrical midpoint of said frame aerial circuit to ground, means for coupling said non-resonant vertical aerial inductance to said last named inductance, a connection between one terminal of said capacity and the control electrode of said relay tube, a connection between the cathode of said relay tube and ground, and a radio receiver connected between the anode and cathode electrodes of said relay tube.

6. In a directional aerial system, in combination, a directional frame aerial comprising one or more convolutions of conducting material closed through a tuning capacity, a connection between a point on said convolutions and ground, said connection including a coupling element, a detuned vertical antenna, said antenna including a coupling element adjustably coupled to the coupling element in said ground connection, and thermionic amplifying means having its input electrodes connected between a point on. said convolutions and ground. I

* E'I'IORE BELLINI. 

